The Hog Louse 649 



The last data relate to a female reared in captivity. Three days after 

 the last molt, when put on the arm to feed, she moved rapidly about 

 for thirty minutes, repeatedly elevating the posterior end of the abdomen, 

 and made no attempt to draw blood. She was returned to the vial and 

 two hours later was given another opportunity to feed, when an egg was 

 found attached to a bristle in the vial. Twice a male was placed in the 

 vial for some hours, but in neither case was copulation seen to occur. 

 During a period of sixteen days eighteen eggs were laid, none of which 

 hatched. The female died six days after laying the eighteenth egg, and 

 gross dissection showed the ovaries very much shrunken. That oviposition 

 continues without fecundation has been observed by various workers, 

 and the unfertilized eggs are easily recognizable because they quickly 

 change color and shrivel up. 



When laid, the egg is an iridescent pearly white. As development 

 progresses it becomes more opaque, and toward the end of the incubation 

 period it appears light amber in color. Its average length is 1.5 to 1.7.5 

 millimeters, and its average breadth at the widest part is 0.5 to 0.75 milli- 

 meter. It is symmetrical, tapers posteriorly, and is bluntly rounded at the 

 anterior end, where the operculum is situated. The widest part is just behind 

 the operculum (Plate LVIII, 2). The surface is covered with small puncta- 

 tions, which are somevv'hat larger on the operculum than on the main part 

 of the egg. The junction of the egg with the operculum is indicated by a 

 small ridge bearing striations parallel to the longitudinal axis of the egg. 



Hatching has not been olDserved, but eggs have been seen shortly after 

 being hatched. The operculum opened away from the bristle and remained 

 attached to the egg by a small hinge; protruding from the egg was a small 

 fragment of the vitelline membrane (Plate LVIII, 2). A number of authors 

 have mentioned points in connection with the hatching of pediculi infesting 

 man, and Sikora (1915:530) was the first to give a short description of 

 the process, which has since been confirmed and extended by Nuttall 

 (1917 d: 148). Probably in the hog louse the process is essentially the 

 same. The following data show that the period of incubation is influenced 

 by temperature, and suggest a reason for the seasonal variation in the 

 development of the eggs on the hog: 



Conditions Eggs hatched after Authority 



On hog About 5 days Coburn^ 



< Data from Coburn (1888). 



